Description

Blit sets dest as the render target, sets source_MainTex property on the
material, and draws a full-screen quad.

Note that if you want to use depth or stencil buffer that is part of the source (Render)texture,
you'll have to do equivalent of Blit functionality manually - i.e. Graphics.SetRenderTarget
with destination color buffer and source depth buffer, setup orthographic projection (GL.LoadOrtho),
setup material pass (Material.SetPass) and draw a quad (GL.Begin).